python3Packages.twine: rely on importlib-metadata unconditionally

Changed from conditional to unconditional in
https://github.com/pypa/twine/commit/22aaa04a88780cfc67fc0e5b80eab9784e81c982

pkgs/development/python-modules/twine/default.nix

@@ -24,6 +24,7 @@ buildPythonPackage rec {
 
   nativeBuildInputs = [ setuptools_scm ];
   propagatedBuildInputs = [
+    importlib-metadata
     keyring
     pkginfo
     pyblake2
@@ -33,7 +34,7 @@ buildPythonPackage rec {
     tqdm
     colorama
     rfc3986
-  ] ++ lib.optionals (pythonOlder "3.8") [ importlib-metadata ];
+  ];
 
   # Requires network
   doCheck = false;